1. Field of the Invention
The present invention relates to a grommet, and in particular to a grommet for mounting on a wire harness used in vehicles. After being mounted on its wire harness, the grommet is inserted into a through-hole formed in a vehicle body panel. The grommet of the invention thus secures the protection of the wire harness, as well as providing water and dust sealing at the periphery of the through-hole.
2. Description of Background Information
A wire harness passing from the vehicle engine compartment to the passenger compartment is commonly equipped with a grommet. Such a grommet is mounted into a through-hole formed in the body panel that separates the passenger compartment from the engine compartment. The grommet thus protects the wire harness placed in the through-hole, and further prevents water, dust and noise from entering into the passenger compartment from the engine compartment.
These grommets are preferably capable of being installed into the through-hole with reduced pushing force and of being held therein firmly after their installation.
A variety of grommets of this type have been proposed until now, including that disclosed in patent document JP-A-2003-32855 (see FIG. 1).
The grommet 1 shown in FIG. 1 includes a funnel-shaped portion 2 having a narrowed end (having a smaller diameter) and an enlarged end (having a larger diameter), and a tubular portion 3 which extends from the narrowed end of the funnel-shaped portion 2.
A circular groove 4 is provided on the external face near the enlarged end of the funnel-shaped portion 2. The circular groove portion 4 can engage with the rim of a receiving hole formed in the body panel. The circular groove portion 4 includes a groove 4a, a first groove wall section 4b located so as to face the narrowed end and a second groove wall section 4c located so as to face the enlarged end.
A wire harness W/H is then passed through the grommet 1 from the side of tubular portion 3 and into the internal space of the funnel-shaped portion 2. The tubular portion 3 is then wrapped with a tape T.
When installing the grommet 1 into the through-hole H in the body panel P, the tubular portion 3 of the grommet 1 is inserted into the through-hole H from the engine compartment side. When the funnel-shaped portion 2 comes into contact with the circular rim of the through-hole H, it is forcibly pushed, so that the funnel-shaped portion 2 is squashed inwardly and passed into the through-hole H. After the passage, the circular groove portion 4 of the grommet 1 engages with the through-hole H of the body panel P, such that the body panel is firmly held from both sides by the first and second groove wall sections 4b and 4c. 
Further, the portion adjacent to the first groove wall section 4b is made thicker than the frusto-conical wall section of the funnel-shaped portion 2, so that the grommet 1 can be held more firmly when engaged with the body panel P.
However, the thickened portion of the above grommet 1 tends to resist to squashing when installed into the through-hole H, thus requiring a stronger insertion force and making the mounting operation more difficult.
If the first groove wall section 4b is made thinner to avoid such problem, although the insertion force shall be lowered, the grommet will be held less firmly once installed.
An object of the invention is to provide a grommet which can be engaged with the body panel with a reduced force, while being held therein with sufficient force.
To this end, there is provided a grommet with an axis adapted to contain a wire harness and insertable into a through-hole formed in a vehicle panel, the grommet including a tubular portion and a funnel-shaped portion, the latter including, sequentially from the tubular portion, a narrowed end section, a frusto-conical wall with external and internal faces, and an enlarged end section that includes an external face provided with a circular groove portion, wherein:
the circular groove portion forms a circular ridgeline at a position nearest to the tubular portion, the frusto-conical wall includes a thin wall section having a substantially uniform thickness and extending from the narrowed end section up to about half way position along the axis in the frusto-conical wall, and a thick wall section having a substantially uniform internal radius and extending from the half way position to and through the enlarged end section along the axis; and
the external face of said frusto-conical wall includes a plurality of shallow recesses which are arranged at a given interval therebetween around the circular direction and which extend from the narrowed end section towards the circular ridgeline, the shallow recesses leading to deep recesses near the circular ridgeline, whereby protrusions are formed adjacent to the shallow and deep recesses.
Preferably, each of the deep recesses has a base extending substantially parallel to the axis and an end wall rising substantially perpendicularly to the axis.
Preferably still, each of the shallow recesses has substantially the same width along the extending direction, whereby each of the protrusions has a width narrowing towards the tubular portion.
Preferably yet, the circular groove portion has a circular wall which inclines from the circular ridgeline radially inwardly in the direction going away from the tubular portion.
Suitably, the enlarged end section has an end face having a central opening with a peripheral rim; from the rim extends a second tubular portion which has a determined length and includes a corrugated section along the length, and an end section; from the end section extends a second funnel-shaped portion having a narrowed end section and an enlarged end section having an external face; and wherein the external face is provided with a second circular groove portion, whereby the grommet can contain a wire harness wired between two body panels.
The invention also relates to a wiring harness including a group of electrical wires and at least one grommet surrounding a length portion of the group, the grommet including an axis adapted to contain a wire harness and insertable into a through-hole formed in a vehicle panel, the grommet including a tubular portion and a funnel-shaped portion, the latter including, sequentially from the tubular portion, a narrowed end section, a frusto-conical wall with external and internal faces, and an enlarged end section that includes an external face provided with a circular groove portion, wherein:
the circular groove portion forms a circular ridgeline at a position nearest to the tubular portion, the frusto-conical wall includes a thin wall section having a substantially uniform thickness and extending from the narrowed end section up to about half way along the axis in the frusto-conical wall, and a thick wall section having a substantially uniform internal radius and extending from the half way position to the enlarged end section along the axis; and
the external face of the frusto-conical wall includes a plurality of shallow recesses which are arranged at a given interval therebetween around the circular direction and which extend from the narrowed end section towards the circular ridgeline, the shallow recesses leading to deep recesses near the circular ridgeline, whereby protrusions are formed adjacent to the shallow and deep recesses.
Preferably, the enlarged end section has an end face having a central opening with a peripheral rim; from the rim extends a second tubular portion which has a determined length and includes a corrugated section along the length, and an end section; from the end section extends a second funnel-shaped portion having a narrowed end section and an enlarged end section having an external face; and wherein the external face is provided with a second circular groove portion, whereby the grommet can contain a wire harness wired between two body panels.
The invention further relates to a method of providing a sealed passage for a wire harness through a panel, including:
forming a through-hole in the panel at a location where the sealed passage is to be provided, the through-hole having rim,
providing a grommet having an axis adapted to contain the wire harness and insertable into a through-hole formed in a vehicle panel, the grommet including a tubular portion and a funnel-shaped portion, the latter including, sequentially from the tubular portion, a narrowed end section, a frusto-conical wall with external and internal faces, and an enlarged end section that includes an external face provided with a circular groove portion, wherein:
the circular groove portion forms a circular ridgeline at a position nearest to the tubular portion, the frusto-conical wall includes a thin wall section having a substantially uniform thickness and extending from the narrowed end section up to about half way position along the axis in the frusto-conical wall, and a thick wall section having a substantially uniform internal radius and extending from the half way position to the enlarged end section along the axis; and
the external face of the frusto-conical wall includes a plurality of shallow recesses which are arranged at a given interval therebetween around the circular direction and which extend from the narrowed end section towards the circular ridgeline, the shallow recesses leading to deep recesses near the circular ridgeline, whereby protrusions are formed adjacent to the shallow and deep recesses,
passing the wire harness through the axis of the grommet,
passing the grommet into the through-hole from a face of the panel, with the tubular portion entering first, until the circular groove portion engages with the rim.
Suitably, the method further includes:
providing the enlarged end section with an end face having a central opening with a peripheral rim, wherein;
from the rim extends a second tubular portion which has a determined length and includes a corrugated section along the length, and an end section; from the end section extends a second funnel-shaped portion having a narrowed end section and an enlarged end section having an external face; and
providing the external face with a second circular groove portion, whereby the grommet can contain a wire harness wired between two body panels.